中文摘要：

研究了认知无线电系统中认知用户的服务切换.提出一种＂随机单次切换＂策略,并通过构建基于信道叠加的半马尔科夫多信道切换模型,分析认知用户在频谱租用过程中的服务等待时间及切换开销.理论和实验表明,＂随机单次切换＂策略下,认知用户具有更小的服务等待时间和切换开销.

英文摘要：

The cognitive user＇s channel switch process was studied, and a ＂random once switch＂ policy was proposed. Moreover, a channel superposition theory based semi-Markov multi-channel switch model was constructed, to analyze the cognitive user＇s service waiting time and switch overhead during its spectrum leasing process. Theoretical and experimental results show that with the ＂random once switch＂ policy, the cognitive user has a shorter service waiting time and smaller switch overhead.